ci: workflow: add helm e2e tests for plugin manager

[Vaishnav-Dhaval]

Summary

This PR adds Helm e2e tests for plugins repo plugins installed via Helm.

Related Issue

Fixes #4058

Changes

• added e2e-tests/tests/helmPlugins.spec.ts to verify plugins installed via Helm and Manager.
• added tableContains helper method to e2e-tests/tests/headlampPage.ts for table content assertions.
• Updated .github/workflows/build-container.yml to:
  • Set up Helm in the CI environment.
  • Deploy Headlamp using the local chart in a dedicated namespace (headlamp-helm).
  • Configure the Plugin Manager via Helm values to install the Flux plugin from Artifact Hub.
  • Execute the new e2e test against the Helm-installed instance.

Steps to Test

1. Trigger the "Build Container and test" workflow in GitHub Actions.
2. In the build discover and deploy job, check the "Deploy Headlamp via Helm and run plugin manager tests" step.
3. Verify that the helmPlugins.spec.ts test passes, confirming that the Flux plugin is visible in the settings table.

Notes for the Reviewer

• The test uses the Flux plugin from Artifact Hub as a stable, official reference for integration testing.
• I've used a 60-second timeout for the plugin check in the e2e test. This is necessary because the Plugin Manager sidecar needs time to download, extract, and initialize the plugin after the pod starts.
• The Helm deployment uses a NodePort service and a custom baseURL (/headlamp-helm) to ensure routing works correctly in complex deployment scenarios.

[k8s-ci-robot]

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[Copilot]

Pull request overview

Adds CI coverage for Helm-based deployments by installing Headlamp via the local Helm chart with the Plugin Manager enabled, then running a new Playwright e2e test to validate a plugin installed in-cluster is visible in the UI.

Changes:

• Add a new Playwright spec (helmPlugins.spec.ts) to verify a Helm+Plugin Manager installed plugin appears in Settings → Plugins.
• Add a tableContains helper to HeadlampPage for table text assertions.
• Extend build-container.yml to install Helm, deploy the local chart into a dedicated namespace, and run the new e2e test against that instance.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
e2e-tests/tests/helmPlugins.spec.ts	New e2e test targeting Helm-installed Headlamp + plugin manager behavior.
e2e-tests/tests/headlampPage.ts	Adds a helper to assert table contents in Playwright tests.
.github/workflows/build-container.yml	Adds Helm setup + chart install and runs the new Helm plugin-manager e2e test in CI.

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[illume]

It looks like the test is failing in CI. Can you please have a look?

[illume]

Can you please address the open review comments?